A document conveying apparatuses such as a scanner are used for various purposes in various locations such as households and offices, and various types of document conveying apparatuses have been provided in accordance with the purposes. For example, in offices and the like, in order to allow more documents to be conveyed at a time, a so-called document conveying apparatus of a lower side retrieval method is used. In the document conveying apparatus of the lower side retrieval method, a document stacking angle of a document tray for stacking documents is almost horizontal, and documents stacked at a lower position are conveyed in order by a pick roller provided in the document tray.
In order to allow the documents stacked on the document tray to be conveyed in a preferable manner by the pick roller, the document conveying apparatus of the lower side retrieval method is provided with a pick arm for pressing, from above, documents stacked on the document tray. However, when the pressurizing force for pressurizing the documents with the pick arm is too small, the pick roller cannot convey the documents, and thus, when the pressurizing force is too large, the frictional force between the stacked documents increases, which may cause a multi-feed of documents.
A sheet-shaped body conveying apparatus including a separate roller, a separation pad disposed to face the separate roller, a retainer spring pressuring the separation pad, and pressurizing force giving means for further increasing the pressurizing force of the retainer spring is disclosed (see Japanese Laid-open Patent Publication No. H4-266340). In this sheet-shaped body conveying apparatus, as soon as a sheet-shaped body stacked on a stacking base is detected to have passed the position of a sensor disposed at a position in proximity to the upstream side of the separate roller, the pressurizing force giving means pressurizing the retainer spring. The pressurizing operation of the pressurizing force giving means is cancelled as soon as the leading edge of the sheet-shaped body is detected to have passed the position of the sensor disposed at the position in proximity to the upstream side of the reading optical system. Therefore, in the sheet-shaped body conveying apparatus, the pressurizing force giving means is activated to strongly pressurize the separation pad onto the separate roller only when an operation for separating the sheet-shaped body is performed.
A feeding apparatus of a lower side retrieval type having a first pick roller provided with a pick roller having an adjustable applied pressure is disclosed (see Japanese Laid-open Patent Publication No. 2005-170651). A default applied pressure value is set for this pick roller, and the pick roller presses a sheet onto the first pick roller with the default applied pressure value when sheet feeding is started. This feeding apparatus uses a sheet conveying sensor disposed on a sheet conveying path to detect whether a sheet is conveyed or not, and in a case where a picking of a sheet with the first pick roller fails, the applied pressure with the pick roller is controlled to be increased by a predetermined amount.